using awk:

curl -s "ftp://ftp-mouse.sanger.ac.uk/current_snps/mgp.v3.snps.rsIDdbSNPv137.vcf.gz" | gunzip -c |\
awk -F '       ' '($0 ~ /^#/ || $11 ~ /1\/1\:/)'

now, if I use a2p to convert it to perl:

#!/usr/bin/perl
eval 'exec /usr/bin/perl -S $0 ${1+"$@"}'
    if $running_under_some_shell;
            # this emulates #! processing on NIH machines.
            # (remove #! line above if indigestible)

eval '$'.$1.'$2;' while $ARGV[0] =~ /^([A-Za-z_0-9]+=)(.*)/ && shift;
            # process any FOO=bar switches

while (<>) {
    chomp;    # strip record separator
    @Fld = split(' ', $_, -1);
    print $_ if ($_ =~ /^#/ || $Fld[(11)-1] =~ /1\/1\:/);
}

lftp -c 'open -e "zcat mgp.v3.snps.rsIDdbSNPv137.vcf.gz” ftp-mouse.sanger.ac.uk/current_snps/' | perl -ne '{chomp; if (/^#CHROM/) {print "$_\n"; }else {@a = split (/\t/,
$_); print "$_\n" if ($a[0] ==18 and $a[1] >= 12972252 and $a[1] <= 12992948 and $a[10] =~ /^1\/1|^1\|1/); } }' > mm10.129S1.Impact.altHom &